Reliability for IR temp guns is typically vary good. However, the color of the surface will have an impact on the readings...with a solid black surface returning the most accurate readings, and shiny or light colored surfaces being less accurate. Starting at about $30, you'll find IR guns with an adjustable emissivity level...so you can tailor the gun to the surface you are taking readings off of. Additionally, you'll want to look at the distance to spot ratio of the gun you'll be using. The larger the distance to spot ratio, the farther away you can take readings and the more accurate the gun will be when reading from a given spot. For example, a gun with a 15:1 D to S ratio will cast a 1" "read" spot from 15" away. Meaning from 15" away the temperature the gun is displaying is the average temp across a 1" diameter circle. If you want more accurate readings of a smaller spot, you'll need to move the gun closer. For herp owner use, the D:S ratio, or field of view, doesn't matter all that much, as you can typically get the gun close to the measuring spot.
As for reliable brands, its hit or miss. Lots of these things are being made in china now, and there are tons and tons of cheap ones out there. Does this really matter in the end? Probably not...as its duty cycle won't be so strenuous that it will break. I personally own a Sixth Sense LT300, and its a great gun. A bit pricey, but Sixth Sense is a very good brand...and these things have lots of uses outside of basking spot readings. But for something cheaper, you can pick up a small unit from several reptile websites for around $25....though a quick browse through google will return options with more features for around the same money. I can't make any specific recommendations however, as I simply haven't used all that many brands. One with a laser pointer is very nice, as it lets you know exactly where you are taking readings from.
